Tree Biotechnology Research Articles

Perennial challenges and opportunities

Perennial challenges and opportunities

Transformation of poplar (Populus alba) plastids and expression of foreign proteins in tree chloroplasts

Plastid transformation offers several unique advantages compared with nuclear genome transformation, such as high level of transgene expression within plastids, expressing multiple transgenes as operons, lack of position effect due to site-specific transgene integration, and reducing risks of gene flow via pollen due to maternal inheritance of the plastid genome. Plastid transformation has been applied to several herbal species, but as yet there are no applications to tree species. We report here the first successful plastid transformation in a tree species, Populus alba. A vector for plastid transformation of poplar (Populus alba) was constructed, which carried the spectinomycin resistance gene and the green fluorescence protein gene as marker genes. In the regenerated shoots, the site-specific integration of foreign genes and the establishment of a high homoplastomic state were confirmed. Immunoblot analysis and histological observations corroborated the accumulation of green fluorescence protein in chloroplasts. The establishment of a plastid transformation system in poplar provides a novel tool for tree biotechnology.

Important new players in secondary wall synthesis

Secondary walls in wood are the most abundant biomass produced by plants. Understanding how plants make wood is not only of interest in basic plant biology but also has important implications for tree biotechnology. Three recent papers report exciting findings regarding a group of novel glycosyltransferases (GTs) involved in secondary wall synthesis. Because little is known about genes involved in the synthesis of wood polysaccharides other than cellulose, the identification of these GTs is a breakthrough in the molecular dissection of wood formation.

In vitro culture and genetic engineering of Populus spp.: synergy for forest tree improvement

Populus species and hybrids are intensively cultivated as sources of woody biomass for the forest products industry and for reforestation of lowlands in temperate regions of the world. However, the long generation time of trees, the presence of seasonal dormancy and the prolonged period required for evaluation of mature traits are strong limitations for classical breeding and selection. The development of methods for in vitro culture and genetic engineering has increased the possibility of producing poplar genotypes improved in insect pest resistance, herbicide tolerance, growth rate and wood quality, or reduction in undesirable traits. Poplar has become a model system in forest tree biotechnology due to several useful features: small genome size, short rotation cycle, rapid growth rate and ease of vegetative propagation. The combination of molecular techniques and classical breeding will help create forest trees with positive effects on the environment. However, risks associated with the biotechnological applications (concerning the impact on biodiversity, long-term adaptation, transgene inheritance and stability) should be carefully evaluated and field tests performed with transgenic poplar.

Xylem-Specific and Tension Stress-Responsive Expression of Cellulose Synthase Genes from Aspen Trees

Genetic improvement of cellulose biosynthesis in woody trees is one of the major goals of tree biotechnology research. Yet, progress in this field has been slow owing to (1) unavailability of key genes from tree genomes, (2) the inability to isolate active and intact cellulose synthase complexes and, (3) the limited understanding of the mechanistic processes involved in the wood cellulose development. Here I report on the recent advances in molecular genetics of cellulose synthases (CesA) from aspen trees. Two different types of cellulose synthases appear to be involved in cellulose deposition in primary and secondary walls in aspen xylem. The three distinct secondary CesAs from aspen- PtrCesA1, PtrCesA2, and PtrCesA3-appear to be aspen homologs of Arabidopsis secondary CesAs AtCesA8, AtCesA7, and AtCesA4, respectively, based on their high identity/similarity (>80%). These aspen CesA proteins share the transmembrane domain (TMD) structure that is typical of all known "true" CesA proteins: two TMDs toward the N-terminal and six TMDs toward the C-terminal. The putative catalytic domain is present between TMDs 2 and 3. All signature motifs of processive glycosyltransferases are also present in this catalytic domain. In a phylogenetic tree based on various predicted CesA proteins from Arabidopsis and aspen, aspen CesAs fall into families similar to those seen with Arabidopsis CesAs, suggesting their functional similarity. The coordinate expression of three aspen secondary CesAs in xylem and phloem fibers, along with their simultaneous tension stress-responsive upregulation, suggests that these three CesAs may play a pivotal role in biosynthesis of better-quality cellulose in secondary cell walls of plants. These results are likely to have a direct impact on genetic manipulation of trees in the future.

Transgenic trees as tools in tree and plant physiology

Transgenic trees are major products of tree biotechnology. This relatively young field of both plant biotechnology and tree biology concentrates on (1) im- provement of pathogen, pesticide, and stress resistance, (2) manipulation of lignin content and composition, and (3) improvement of growth. Transgenic trees also have a great potential in other areas of applied and environmen- tal research, such as in the production of phytochemicals and in phytoremediation of polluted soils. However, ge- netically modified trees are also excellent tools for phys- iological research. Transgenic trees are indispensable in investigations of the regulation of wood formation, long- distance transport, and tree growth cycles. In addition, transgenic poplars contribute significantly to our under- standing of the regulation of sulfur nutrition. In this re- view we concentrate on the use of transgenic tree species to improve knowledge in tree and, more generally, plant physiology rather than to cover extensively the field of commercial tree biotechnology or the biological safety of transgenic plant release.

植物ゲノムサイエンスの発展と樹木バイオテクノロジー研究 その現状と展望

Progress in molecular biology in the 1980 s brings enable us to analyze various type of biological nature of plants at the molecular (DNA) level. Genetic engineering based on the molecular biological techniques provided exciting opportunity to produce transgenic plants and mutant lines with altered phenotypes and to better understanding the physiology, biochemistry of plants. Furthermore, much of knowledge how plant grow and develop has been gained from research in genome area such as complete genome sequence Arabidopsis thaliana that is being used worldwide as a model organism for basic and applied research in plant biology. Likewise, novel approaches such as express sequence tags, genome sequencing and enhancing traditional strategies for woody plant research. This paper provides a comprehensive overview of tree biotechnology and the areas currently being researched on biosynthesis of cell wall.

Science and Technology Networks in the Canadian Forest Service

The Canadian Forest Service has reorganized its science and technology programs to focus on establishing partnerships and networks, thereby becoming a partner to business, academic institutions, other governments and voluntary organizations to stimulate increased S&T activity. Current policy issues in the forest sector reflect the changing nature of our society and the demands on forests in particular.The CFS has established national networks in the following fields: Effects of Forest Practices, Landscape Management, Climate Change, Fire Management, Socio-Economic Research, Pest Management Methods, Ecosystem Processes, Tree Biotechnology and Advanced Genetics, Biodiversity, and Forest Health.This national network-based approach to deliver its S&T program will allow us to address national and international issues while delivering programs through regional research centres. As the Canadian forest sector competes in world markets, it will have to meet international demands for sustainable forest management. Key words: networks, partnerships, alliances, forest issues

Progress in the biotechnology of trees

An increasing world population and rise in demand for tree products, especially wood, has increased the need to produce more timber through planting more forest with improved quality stock. Superior trees are likely to arise from several sources. Firstly, forest trees can be selected from wild populations and cloned using macropropagation techniques already being investigated for fruit tree rootstocks. Alternatively, propagation might be brought aboutin vitro through micropropagation or sustained somatic embryogenesis, with encapsulation of the somatic embryos to form artificial seeds. Tree quality could be improved through increased plant breeding and it is likely that experienced gained, to date, in the breeding of fruit species will be useful in devising strategies for forest trees. Since the development of techniques to regenerate woody plants from explant tissues, cells and protoplasts, it is now feasible to test the use of tissue culture methods to bring about improvements in tree quality. Success has already been achieved for tree species in the generation of somaclonal and protoclonal variation, the formation of haploids, triploids and polyploids, somatic hybrids and cybrids and the introduction of foreign DNA through transformation. This review summarizes the advances made so far in tree biotechnology, and suggests some of the directions that it might take in the future.

The Biotechnology of Urban Trees

Trees are some of the most difficult plants to manipulate in breeding and improvement programs. Plant biotechnology offers a unique set of tools that allows the plant breeder heretofore unprecedented ability to precisely change and clone such woody perennials. Although the future of biotechnology of trees is revolutionary, there are some major problems that must be solved before the full potential of this technology can be applied to urban tree improvement. Nevertheless, major advances in genetic transformation, cloning, and regeneration of trees have been recorded in the last few years; continued progress will depend on the effort applied to tree biotechnology and to determining the physiological/genetic bases of urban tree growth and ecology.